Tuesday, July 22, 2008

The Accelerating Universe

Since the 1920s, scientists have known that the universe is expanding. Most believe that this expansion has been going on since the Big Bang, estimated to be 12 billion to 15 billion years ago.

But one of the most pressing questions in cosmology (the study of the structure and history of the universe) is whether this expansion will continue forever, or whether gravity will take over, reverse the course, and pull all of the galaxies back together into a Big Crunch, which would signify the end of time as we know it.

Suddenly, in the past two years, something weird has made the question loom even larger: The expansion of the universe, according to two independent studies, seems actually to be accelerating.

"This is completely unexpected," says Morris Aizenman, senior science associate in the National Science Foundation's Mathematical and Physical Science Directorate. "What force is causing that acceleration? We have no answer."

Researchers speculate that the acceleration might be caused by some strange and unknown matter or energy whose force of gravity repels, rather than attracts, over long distances.

More About The Accelerating Universe

Anything that has mass also has gravity, and this force of gravity is exerted across infinite space, decreasing with distance. You, for example, exert a tiny gravitational pull on distant planets and galaxies, and they pull on you.

And so you, your family, this Earth, and our Milky Way galaxy all tug on other galaxies. Eventually, even though the universe is expanding in all directions, the gravity of all the galaxies should slow the expansion, bring it to a halt, and then pull all matter back together.

Unless, somehow, some force can overcome this "normal" gravity.

Over the past decade, scientists have become increasingly convinced that some form of "dark matter" permeates the universe, accounting for phenomena seen in space that could not occur based on the amount of observable matter. But even this dark matter can't account for an accelerating universe.

Instead, some have proposed, there must be small forces at work in even the smallest "empty" spaces, inside your body, in the air and around the universe -- a kind of antigravity which, over long distances, pushes other stuff away.

Meanwhile, while the case for an accelerating universeis very strong, more evidence is needed. But even if it turns out wrong, cosmologists say that the expansion isn't slowing down as fast as it should be, based on what they know about mass and gravity. Something weird is going on.

"More observations need to be made," Aizenman says, adding that whole new theories and explanations will likely result.

NASA's MAP mission, set for launch this spring, will measure small fluctuations in the temperature of a ubiquitous background of cosmic microwave radiation, which is thought to have formed just 500,000 years after the Big Bang. A proposed satellite called SNAP (SuperNova / Acceleration Probe) would map the expansion rate of the universe at epochs varying from the present to 10 billion years ago.

Gathering such information with missions like these is expected to reveal the size, shape, content, age and fate of the universe.

This message has been posted on HMGoogleGroup by: Andy Says
Goto Message, Contact Author, Discuss...


Robert I. Marsh II said...

An excellent article! There is something, that may change how we perceive our Universe! I am hosting a CERN LHC Public Opinion Poll & Debate, at the web-link below. Everyone is welcome to observe, but you must register to Vote! I plan to take these poll results, and forward them to Director General Robert Aymar, Catherine Decosse, Michelangeko Mangano, and even Stephen Hawking! They have already been notified of the Poll 'opening status' and 'In Progress' nature. The Poll closes on October 17, 2008. I could use your honest votes: For/Against/Undecided. This is designed to reflect 'public opinion' for now, and to the future generations to come! Thank You!